This invention relates to an electronic musical instrument of the type in which externally fed piano or like sounds are converted into a digital waveform signal which is stored in a memory, sounds having various waveforms being obtained thereby through control of the addressing of the memory.
Heretofore, an electronic musical instrument has been developed in which a tone of, for instance, C1, obtained by depressing a C1 key of a piano, is converted through a microphone into a C1 tone signal which is A/D converted into a PCM digital signal to be stored in a waveform memory. In order to effectively use the memory area of the waveform memory, the operation of storing the PCM digital signal in the waveform memory is started simultaneously with the depression of a note key such as the C1 note key. With this arrangement, however, it is likely that a leading, rising portion of the piano tone fails to be stored. To overcome this drawback, the operation of storing data in the waveform memory may be started before the key depression. In this case, however, it is necessary to use a waveform memory having a large capacity, leading to a cost increase.
Meanwhile, in the prior art electronic musical instrument noted above, the waveform data stored in the waveform memory is read out under control by a DMAC (direct memory access controller), and waveform data is DMA transferred from the waveform memory to a FIFO (first in first out) buffer every time a key on the keyboard is operated. The waveform data stored in the FIFO buffer is fed to a D/A converter according to the output of a VCO, which provides a frequency signal corresponding to the note of the depressed key, whereby a tone having a predetermined pitch is obtained. The DMA transfer of the waveform data from the waveform memory to the FIFO buffer is done under control of a CPU. In a polyphonic electronic musical instrument where signals are processed through time division basis processing, therefore, the CPU is used exclusively for the DMA processing, such that it can devote insufficient time to other processing.
Further, the polyphonic electronic musical instrument noted above requires pluralities of VCOs, FIFO buffers, D/A converters, etc., so that its price is inevitably high.